High performance tires having relatively thin treads designed for use at high vehicular speeds, such as for example race tires, typically have thin treads of rubber compositions which may contain high contents of a combination of reinforcing carbon black and rubber processing oil. The combination of a high loading of both carbon black and rubber processing oil in the tread rubber composition is provided in order to promote traction for the running surface of the tire tread for such tires intended for high speed operation.
However, the high loading of the combination of carbon black and processing oil in the tread rubber makes the thin tire tread more hysteretic with a greater propensity for internal heat generation, and resultant temperature increase of the tread rubber itself, at high vehicular speeds than a significantly lower loading of a combination of carbon black and rubber processing oil.
In particular, the heat buildup within the thin tread with the high loading of the combination of carbon black and rubber processing oil is more related to punishment of the thin tread against the road at high vehicular speeds than a heavy duty tire with a thick tread which is intended for heavy duty use under heavy vehicular loads pressing the thick tire tread onto the road surface at significantly slower vehicular speeds. Thus the problem of internal heat buildup for such high speed designed thin tire treads is of a different character than that of the indicated thick treaded heavy duty tires.
For this invention, the thin tire tread is of a rubber composition highly loaded with oil and a selected carbon black comprised of a conductive carbon black and optionally a classical rubber reinforcing carbon black and optionally containing a precipitated silica which is considered herein to promote high performance of the tire in a sense of traction of the tread running surface and to promote a heat conductive path from the tread to its running surface as the tire is being run under operating conditions, namely at a high vehicular speed.
In practice, the classical rubber reinforcing carbon black and/or precipitated silica reinforcing filler used in combination with a high content of rubber processing oil is provided to promote a higher hysteresis (e.g. lower rebound physical property) to promote traction for the thin rubber tread's running surface.
Historically, tires have been taught to be provided with various combinations of carbon blacks for various purposes. For example, see U.S. Pat. Nos. 5,798,405, 5,430,087, 5,780,537 and 6,053,226 and U.S. Patent Application No. 2005/0159535 A1.
In U.S. Patent Application No. 2005/0159535 A1, a heavy duty tire tread having a thick tread of at least 4 centimeters is provided with a combination of diverse carbon blacks to provide greater heat conductivity for the heavy duty tire tread and reduce its internal heat generation created under heavy loads for the tire. The tire tread of this invention differs significantly from such thick heavy duty tread in a sense that the thin tire tread of this invention designed to promote traction for the tread's running surface at high vehicular speeds and the significantly thicker tire tread of U.S. Patent Application No. 2005/0159535 A1 is designed to promote road hazard durability and resistance to tread wear for a tire intended to be run under slower speeds and carry significantly higher vehicular loads.
In the description of this invention, the terms “rubber” and “elastomer” where used, may be used interchangeably, unless otherwise prescribed. The terms “rubber composition”, “compounded rubber” and “rubber compound”, where used, may be used interchangeably to refer to “rubber which has been blended or mixed with various ingredients and materials” and such terms are well known to those having skill in the rubber mixing or rubber compounding art.
In the description of this invention, the DBP absorption values for carbon blacks is a dibutylphthalate value expressed in terms of cc/100 grams (or cm3/100 grams) according to ASTM D2414. The Nitrogen Surface Area (referred to herein as “NSA”) value is expressed in terms of square meters per gram (m2/g) according to ASTM D3037.